Many drugs and chemical agents are known to be effective in treatment of diseased tissue, such as tumors. However, such agents also often have deleterious side effects when introduced into the organism in sufficient dosage to treat the targeted tissue.
One attempt to selectively treat diseased tissue, such as tumors, is development of chemical agents which selectively affect only tumor cells. However, such chemical agents typically are only partially selective for the diseased tissue and often have a deleterious effect on healthy cells. Another attempt to selectively treat diseased tissue is to inject the chemical agent directly into the diseased tissue mass. However, the effect of chemical agents on diseased tissue is often dependent upon delivery of the chemical agent across cell membranes of the cells in the tissue mass as opposed to simply injecting the chemical agent into the tissue. Further, chemical agents which are injected into diseased tissue typically enter the bloodstream and are transported away from the targeted tissue mass before they have a significant therapeutic affect on the tissue mass into which they were injected.
Another attempt to selectively treat diseased tissue is by electroporation. Generally, electroporation is a method of increasing the permeability of tissue and cell membranes. The increased permeability allows transport, or migration, of chemical agents through the tissue or across cell membranes into cells. For example, electroporation can include applying a voltage across tissue in vitro to cause the permeability of the tissue and cell membranes of cells in the tissue to increase. If the tissue is in the presence of a suitable chemical agent, the chemical agent can then migrate across the tissue or into cells of the tissue. Electroporation has also been used to deliver drugs to tissue, in vivo, by applying electrodes to the surface of an organism and applying a voltage between the electrodes which exposes the tissue to an electric field. The tissue thereby becomes electroporated and allows delivery of a chemical agent, such as a drug, which has been applied either topically to the organism or injected into the blood stream of the organism, across the electroporated tissue and into cells of the electroporated tissue.
However, in vivo electroporation is generally limited to tissue which is proximate to the surface of the organism. For example, tissue requiring delivery of a drug or other chemical agent in vivo is limited to tissue which is close to the skin of the organism where the electrodes are disposed. Therefore, tissue which would otherwise be treatable by drug delivery or chemotherapy, such as tumors, are relatively unaffected by known methods of electroporation.
Therefore, a need exists for a new method and apparatus for treating remote tissue, in vivo, which overcomes or minimizes the above-listed problems.